Dogfish population being rebuilt

Friday

A dogfish might not be quite the pest locusts are but from fishermen to scientists to government officials, wanted to see more dogfish taken.

Are local fisheries going to the dogs?

Some people in the business think so. In point of fact, the spiny dogfish has been classified as over fished, and thus under federal protection since 1998, but they aren’t nearly over fished enough in some minds.

“Managing the field for locusts is just nuts,” opined Robert Fitzpatrick, a fish broker with Maguro America in Chatham. “Guess what? They’re not going to go extinct. It will be a terrible thing if a snorkeler can’t see a pile of dogfish? Why do we want them?”

A dogfish might not be quite the pest locusts are but most everyone at the Spiny Dogfish Shark Forum, at the Holiday Inn in Hyannis, from fishermen to scientists to government officials, wanted to see more dogfish taken.

Dogfish eat other fish, sometimes right off the hook or out of the net. Estimates of dogfish predation on one-year-old cod made in 1998 were for 2.15 million fish, out of a total population of 5.77 million. That’s 37 percent of the juvenile cod population.

“Although the amount of cod predation is minimal compared to other fish (around 5 percent of the diet), two million is a lot of cod,” admitted Dr. David Pierce of the Division of Marine Fisheries.

Codfishing is under heavy regulation in an effort to build up stocks. The dogfish seem to be on the other side of the equation.

“A small scale (dogfish) fishery would remove one of the major predators of sea herring (68,000 metric tons (848 million fish) a year,” Pierce added. “Dogfish are not over fished so we need to take a precautionary approach to fisheries management in regard to cod. We should err on the side of cod rebuilding, not on dogfish rebuilding.”

The dogfish population is being rebuilt, however. Prior to 1979 there was minimal interest in dogfish in the United States. However, offshore Russian trawlers were hauling in as much as 23,000 metric tons year. If you ate fish and chips in the U.K., you were eating dogfish.

The foreign ships disappeared after the United States enacted a 200-mile limit in 1976 and the U.S. take jumped from 73 metric tons in 1972 to a peak of 27 million in 1996. Based on low estimates of pups (young dogfish), the fishery was designated as over fished by the federal government in 1998. A target, for sustained reproduction, of 200,000 metric tons of spawning size female dogfish was set.

“It dipped down to 40,000 metric tons (in 1999) and the latest estimate is from ’06 informed by the ’07 survey, 140,000 metric tons,” explained fishery analyst James Armstrong of the Mid-Atlantic Fishery Management Council. “What scientists think is that the 40,000 was an underestimate.”

Estimating the number of dogfish has proved problematic. Earlier surveys suggest that there are six times as many males as females. But that could be a factor of where and when the samples were taken. Recent studies also have shown dogfish to be natural ramblers, not the stay-at-home types they were thought to be. All of which means there could be a lot more dogfish out there causing a lot more problems.

“Dogfish are voracious and opportunistic. They’ll eat anything around them,” declared Dr. James Sulikowski, a fish biologist at University of New England. “Dogfish consume 1.5 percent of their body weight a day.”

Doing some math: if there are 478,000 metric tons of dogfish out there, which is one estimate, and they eat six times their body weight a year, that comes to 2.4 million metric tons of food. Looking at the stomach contents of 401 dogfish, Sulikowski found 93 percent of their diet was fish, mostly cod, haddock, hake, herring and sand lances.

“So what are dogfish doing to commercial fishing grounds?” he wondered.

“People cannot fish for other species, in particular bluefin tuna,” said Fitzpatrick, the fish broker in Chatham, who markets tuna to Japan. “And it’s as if you had a second fleet fishing for the herring.”

Dogfish will eat the bait off the tuna hooks.

“Let 10,000 wolves out in Yellowstone and all of a sudden they’re scratching their heads wondering why the deer aren’t doing well,” Fitzpatrick noted. “Why not cut back mortality in juvenile cod by 40 percent by killing a pile of dogfish?”

Dogfish can be fished, the bellies are shipped to Germany, but the current federal limit is 600 pounds per trip.

“Not enough to pay for gas,” Armstrong noted. “The trip level is so low because it’s only meant to allow for the return of bycatch.”

In shore, fishermen can catch 3,000 pounds a trip. Coast-wide the federal limit is 8 million tons. That’s divided into two seasons. New England gets 58 percent of that quota, so for the summer season, which began May 1, the New England quota is 1,684,000 pounds and the season will be closed when that is reached. As of May 21, the tally was 146,943 pounds with 9,130 of those from Massachusetts’ waters.

The scientists who spoke agreed with Fitzpatrick, there seem to be more dogfish than the estimates indicate.

“Spiny dogfish tend to be everywhere in the Gulf of Maine in tremendous numbers,” Pierce said.

Dogfish are supposed to migrate south to the Carolinas in the winter.

“But one fisherman discarded 7,000 pounds of dogfish on Dec. 15. So the fish are here. They are not moving,” Sulikowski observed. Or they’re moving a lot.

Sulikowski caught and tagged three dogfish with $5,000 satellite tags.

“You get great data from it,” he said.

Indeed. Standard tags, recovered at the end of the fish’s travels would have indicated one dogfish traveled a modest distance off the shore of Long Island. Detailed satellite data revealed a footloose traveler, who journeyed south to the Delaware, north around Nova Scotia to Prince Edward Island and looped back and forth within the span over a three-month period.

“These fish are moving all over the place. They are not doing what we thought,” Sulikowski said. “They’re in every ecosystem, offshore, inshore, feeding on all types of commercial fish. The fish are also moving down and up the water column. Much of the time they are in the upper portion of the water.”

If you are trawling the bottom for dogfish, you may be missing them. Or if your favorite fish is doing his tourist thing off Prince Edward Island when you do your population check, your estimates could be off.

“They go out and check the oil in the ecosystem and there’s never anything on the dipstick,” complained Fitzpatrick.

Pups can also be born throughout the year.

“The population estimates are probably low,” Sulikowski conceded.

Dogfish do seem to be very abundant in the cod conservation zone north of Boston.

“There is an overlap of dogfish and small codfish near Massachusetts shores,” Pierce said. “It is probable that rebuilding dogfish numbers could impede efforts to revive the cod population. Unfortunately, the dogfish management plan is silent on this issue. Dogfish is a single species plan with multiple species implications.”

“The law addresses single populations so if a single population drops down below a certain level, it is over fished,” Armstrong explained. “Then the law mandates a rebuilding plan for that species.”

Considering multiple species isn’t yet in the program.

“That level of management is still many years in the future, which is unfortunate,” said Armstrong. “We’re still on a single species assessment mentality and it ain’t working.”

“We’re still in our infancy as far as ecosystem based management,” Pierce said. “It’s possible the (new) guidelines may be so restrictive we will not be able to factor in ecological considerations.”

However the quota has been raised, it was 6 million pounds a few years ago. It will be reassessed for next year. Pierce would like to see regional quotas replaced by state-by-state limits.

“This is an extremely important relationship for us to understand,” Pierce said.

“If we don’t fix what is upside down, we’re never going to fix this, this is insane,” Fitzgerald concluded.

The Cape Codder

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